Rim Brakes vs. Disc Brakes
03-28-13, 02:27 PM
#26
Senior Member
Lots of good solid discussion here on this topic. While I agree with most everyones points, I don't think I have changed or not changed my thinking on brakes for 2bikes. The more braking capacity the better up to the practical limits of cost, weight, and ability to actuate them.
As I have post plotted several times of recent, my next 2bike frame build with have mounts for mechanical disks on both ends as well as studs for canti's at both ends. That will be a little over the top since my current tandems stop well enough with dual canti's plus a rear drum drag brake. But then again I plan to take the rest of the design over the top (like to have 4x10 gearing, probably 160/125mm F/R OLDs, fully internal cabling and wiring, probably IPS/ICS, embedded alternator(s) with a rechargable in-line battery pack, very bright but focused full tilt lighting set, matching custom racks, full baggage set, a new design custom Bob trailer pivoting off a 5th like mount in the seat post area, matching custom fenders, etc, so why not take the brakes over the top also. The torch giveth, the road taketh away.
/K
As I have post plotted several times of recent, my next 2bike frame build with have mounts for mechanical disks on both ends as well as studs for canti's at both ends. That will be a little over the top since my current tandems stop well enough with dual canti's plus a rear drum drag brake. But then again I plan to take the rest of the design over the top (like to have 4x10 gearing, probably 160/125mm F/R OLDs, fully internal cabling and wiring, probably IPS/ICS, embedded alternator(s) with a rechargable in-line battery pack, very bright but focused full tilt lighting set, matching custom racks, full baggage set, a new design custom Bob trailer pivoting off a 5th like mount in the seat post area, matching custom fenders, etc, so why not take the brakes over the top also. The torch giveth, the road taketh away.
/K
03-28-13, 02:51 PM
#27
Senior Member
Look at it this way...
When driving or braking loads are applied at the hub of a spoked wheel, there is an uneven amount of torque applied to only 1/2 of the spokes, i.e., the "pulling spokes" if you will.
When rim brakes are applied there is an equal amount of loading applied to both the pulling and trailing spokes that, in effect, cancel each other out, i.e.,t there is no torque on the spokes.
The easiest way to visualize this is to think about a radially spoked front wheel where there are no pulling or trailing spokes. Rim brakes work just fine with a radially spoked front wheel because of the cancelling effect of the forces coming from the stopping action of the rim brake at one edge of the rim against the forces coming from the tire contact patch with the road, i.e, the rim carries the load.
Now imagine if you will what would happen to a radially spoked front wheel if a disc brake were used or, if it would help, imagine what would happen if you tried to use a radially spoke rear wheel when power is applied to the rear wheel via a chain driven sprocket at the hub. All of the spokes are going to be "pulled" at the hub as they work against the rim/tire contact patch with the road.
When driving or braking loads are applied at the hub of a spoked wheel, there is an uneven amount of torque applied to only 1/2 of the spokes, i.e., the "pulling spokes" if you will.
When rim brakes are applied there is an equal amount of loading applied to both the pulling and trailing spokes that, in effect, cancel each other out, i.e.,t there is no torque on the spokes.
The easiest way to visualize this is to think about a radially spoked front wheel where there are no pulling or trailing spokes. Rim brakes work just fine with a radially spoked front wheel because of the cancelling effect of the forces coming from the stopping action of the rim brake at one edge of the rim against the forces coming from the tire contact patch with the road, i.e, the rim carries the load.
Now imagine if you will what would happen to a radially spoked front wheel if a disc brake were used or, if it would help, imagine what would happen if you tried to use a radially spoke rear wheel when power is applied to the rear wheel via a chain driven sprocket at the hub. All of the spokes are going to be "pulled" at the hub as they work against the rim/tire contact patch with the road.
my perception is that with a caliper brake applying stopping power to the rim you have in effect a large diameter disc brake and the only real issue is potential heat build up which could cause a tire failure in an extreme condition.
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